1. Field:
Subject matter disclosed herein relates to monitoring blood glucose levels in patients.
2. Information:
The pancreas of a normal healthy person produces and releases insulin into the blood stream in response to elevated blood plasma glucose levels. Beta cells (β-cells), which reside in the pancreas, produce and secrete insulin into the blood stream as it is needed. If β-cells become incapacitated or die, a condition known as Type 1 diabetes mellitus (or in some cases, if β-cells produce insufficient quantities of insulin, a condition known as Type 2 diabetes), then insulin may be provided to a body from another source to maintain life or health.
Traditionally, because insulin cannot be taken orally, insulin has been injected with a syringe. More recently, the use of infusion pump therapy has been increasing in a number of medical situations, including for delivering insulin to diabetic individuals or trauma patients. As of 1995, less than 5% of Type 1 diabetic individuals in the United States were using infusion pump therapy. Presently, over 7% of the more than 900,000 Type 1 diabetic individuals in the U.S. are using infusion pump therapy. The percentage of Type 1 diabetic individuals that use an infusion pump is growing at a rate of over 2% each year. Moreover, the number of Type 2 diabetic individuals is growing at 3% or more per year, and growing numbers of insulin-using Type 2 diabetic individuals are also adopting infusion pumps. Additionally, physicians have recognized that continuous infusion can provide greater control of a diabetic individual's condition, so they too are increasingly prescribing it for patients.
External infusion pumps are typically to control a rate of insulin infusion based, at least in part, on blood glucose measurements obtained from metered blood glucose samples (e.g., finger stick samples) or from processing signals received from a blood glucose sensor attached to a patient to provide sensor glucose measurements. By processing signals from such a blood glucose sensor, a patient's blood glucose level may be continuously monitored to reduce a frequency of obtaining metered blood glucose sample measurements from finger sticks and the like. However, measurements of blood glucose concentration obtained from processing signals from blood glucose sensors may not be as accurate or reliable as metered blood glucose sample measurements obtained from finger stick samples. Also, parameters used for processing blood glucose sensors for obtaining blood glucose measurements may be calibrated from time to time using metered blood glucose sample measurements as reference measurements obtained from finger sticks and the like. Accordingly, techniques for sensor-based continuous blood glucose monitoring typically still incorporate metered blood glucose sample measurements obtained from finger sticks and the like.
The so-called Yale Protocol provides one technique for determining a frequency for determining insulin infusion rates and time intervals between metered blood glucose sample measurements for insulin infusion therapy for a wide range of patients. Examples of the Yale Protocol may be found in Goldberg P A, Siegel M D, Sherwin, R S, et al. “Implementation of a Safe and Effective Insulin Infusion Protocol in a Medical Intensive Care Unit”, Diabetes Care 27(2):461-467, 2004, and Goldberg P A, Roussel M G, Inzucchi S E. “Clinical Results of an Updated Insulin Infusion Protocol in Critically Ill Patients”, Diabetes Spectrum 18(3):188-191, 2005. Regarding time intervals between metered blood glucose sample measurements, the Yale Protocol may specify a time between metered blood glucose sample measurements based on a currently observed blood glucose concentration and a rate of change at a last reference check.